The present invention relates to an improved base assembly which may be used in flat panel displays. More particularly, the present invention relates to highly planar base assemblies used in flat panel field emission displays, and techniques for producing such base electrodes.
Known techniques for manufacturing field emission displays (FEDs) may utilize a process known as chemical-mechanical planarization (CMP), which is also sometimes referred to as chemical-mechanical polishing. The use of a chemical-mechanical planarization process in manufacturing a field emission display as disclosed, for example, in commonly owned U.S. Pat. No. 5,186,670 issued Feb. 16, 1993 to Doan et al. and U.S. Pat. No. 5,372,973 issued Dec. 13, 1994 to Doan et al. Further details of a chemical-mechanical planarization process are disclosed, for example, in commonly-owned U.S. Pat. No. 5,232,875 issued Aug. 3, 1993 to Tuttle et al. These patents are hereby incorporated by reference in their entirety.
A typical chemical-mechanical planarization process utilizes a polishing pad which planarizes an underlying work piece such as a semiconductor wafer by mechanical force. A chemically active slurry which carries an abrasive element may be utilized in conjunction with the polishing pad to improve the polishing performance. However, other mechanical planarization techniques may utilize an abrasive element carried directly in the polishing pad rather than in the slurry. Additionally, mechanical planarization techniques may utilize fluids which do not include a chemically active component.
Certain situations previously encountered in the manufacture of flat panel field emission displays with a mechanical planarization step presented difficulties. For example, if the structure of the underlying work piece is not sufficiently planar prior to polishing, the mechanical planarization step may have a tendency to round off comers of features on the field emission display base assembly or, possibly, to unintentionally penetrate completely through a layer of the field emission display base assembly. If a mechanical planarization step is used on an excessively non-planar work piece, problems may arise, for example, with oxide dielectric layers. Mechanical stress from the planarization of a nonplanar workpiece may cause damage to dielectric layers, leading to possible dielectric breakdown. Problems can also arise with conductive layers, particularly if conductors are severed or if leakage pads are formed. All of this, of course, adversely impacts on the quality of the resultant field emission display and may require portions of a production lot to be scrapped. As a result, production yields are reduced and manufacturing expenses increased.
Accordingly, there is a need for a base assembly for use with a flat panel field emission display which permits improved results from a mechanical planarization step such as chemical-mechanical planarization. It is a primary objective of the present invention to provide such a base assembly, and a technique for producing such a base assembly.